Method for measuring changes in osmotic pressure

Abstract

A method is provided which allows for monitoring changes in osmotic pressure of a sample as a function of time and/or temperature. This is accomplished by placing a sample of a solution at an initial temperature into the sample cell above the membrane supported in the sample cell; sealing the sample in the sample cell; introducing gas at an elevated pressure to the sample cell to generate a dialyzate by allowing a portion of the solution to dialyze through the membrane; varying the elevated pressure of the gas until equilibrium across the membrane is substantially achieved; changing the temperature of the solution over time; measuring the osmotic pressure at predetermined intervals of time; and calculating the changes in the osmotic pressure. Alternatively, the method for monitoring changes in osmotic pressure of a sample (wherein the changes are the result of a chemical reaction generated in the sample cell) can be practiced by placing a sample of a solution at an initial temperature into a sample cell above a membrane supported in the sample cell; adding reactants to the sample; sealing the sample and reactants in the sample cell; introducing gas at an elevated pressure to the sample cell to generate a dialyzate by allowing a portion of the solution to dialyze through the membrane; varying the elevated pressure of the gas until equilibrium across the membrane is substantially achieved; measuring the osmotic pressure at predetermined intervals of time; and calculating the changes in the osmotic pressure.

What is claimed is:  
     
       1. A method for monitoring changes in osmotic pressure of a sample as a function of time comprising the steps of: 
       (a) placing a sample of a solution at an initial temperature into a sample cell above a membrane supported in the sample cell;  
       (b) sealing the sample in the sample cell;  
       (c) introducing gas at an elevated pressure to the sample cell to generate a dialyzate by allowing a portion of the solution to dialyze through the membrane and enter a transparent dialyzate exit tube connected to sample cell;  
       (d) varying the elevated pressure of the gas to obtain a substantially stationary dialyzate meniscus in the transparent dialyzate exit tube indicating osmotic pressure equilibrium;  
       (e) changing the temperature of the solution over time;  
       (f) measuring the elevated gas pressure at predetermined intervals of time, the osmotic pressure being equal to the elevated pressure; and  
       (g) calculating the changes in the osmotic pressure.  
     
     
       2. A method for monitoring changes in osmotic pressure of a sample as a function of time comprising the steps of: 
       (a) placing a sample of a solution at an initial temperature into a sample cell above a membrane supported in the sample cell;  
       (b) sealing the sample in the sample cell;  
       (c) introducing gas at an elevated pressure to the sample cell to generate a dialyzate by allowing a portion of the solution to dialyze through the membrane and enter a transparent dialyzate exit tube connected to the sample cell;  
       (d) varying the elevated pressure of the gas until equilibrium across the membrane is substantially achieved;  
       (e) indicating osmotic equilibrium across the membrane with a substantially stationary dialyzate meniscus in the transparent dialyzate exit tube;  
       (f) changing the temperature of the solution over time;  
       (g) measuring the osmotic pressure at predetermined intervals of time; and  
       (h) calculating the changes in the osmotic pressure.  
     
     
       3. A method as recited in claim  1  further comprising the step of: 
       (a) suspending a starrier bar above the membrane; and  
       (b) stirring the sample in the sample cell with the stirrer bar.  
     
     
       4. A method as recited in claim  2  further comprising the step of: 
       (a) suspending a stirrer bar above the membrane; and  
       (b) stirring the sample in the sample cell with the stirrer bar.  
     
     
       5. A method for monitoring changes in osmotic pressure of a sample as a function of time comprising the steps of: 
       (a) placing a sample of a solution at an initial temperature into a sample cell above a membrane supported in the sample cell;  
       (b) adding reactants to the sample;  
       (c) sealing the sample and reactants in the sample cell;  
       (d) introducing gas at an elevated pressure to the sample cell to generate a dialyzate by allowing a portion of the solution to dialyze through the membrane;  
       (e) varying the elevated pressure of the gas until equilibrium across the membrane is substantially achieved, equilibrium being indicated by a substantially stationary dialyzate meniscus in a transparent dialyzate exit tube connected to the sample cell;  
       (f) measuring the osmotic pressure at predetermined intervals of time; and  
       (g) calculating the changes in the osmotic pressure.  
     
     
       6. A method as recited in claim  5  further comprising the step of: 
       (a) suspending a stirrer bar above the membrane; and  
       (b) stirring the sample in the sample cell with the stirrer bar.  
     
     
       7. A method as recited in claim  5  further comprising the step of: 
       maintaining the sample at a constant temperature.  
     
     
       8. A method for monitoring changes in osmotic pressure of a sample as a function of time comprising the steps of: 
       (a) placing a sample of a solution at an initial temperature into a sample cell above a membrane supported in the sample cell;  
       (b) adding reactants to the sample;  
       (c) sealing the sample and reactants in the sample cell;  
       (d) introducing gas at an elevated pressure to the sample cell to generate a dialyzate by allowing a portion of the solution to dialyze through the membrane and enter a transparent dialyzate exit tube open to atmosphere and connected to sample cell;  
       (e) varying the elevated pressure of the gas to obtain a substantially stationary dialyzate meniscus visually observable in the transparent dialyzate exit tube, the substantially stationary dialyzate meniscus indicating osmotic equilibrium across the membrane;  
       (f) measuring the osmotic pressure at predetermined intervals of time; and  
       (g) calculating the changes in the osmotic pressure.  
     
     
       9. A method as recited in claim  8  further comprising the step of: 
       (a) suspending a stirrer bar above the membrane; and  
       (b) stirring the sample in the sample cell with the stirrer bar.  
     
     
       10. A method as recited in claim  8  further comprising the step of: 
       maintaining the sample at a constant temperature.  
     
     
       11. A method as recited in claim  1  wherein: 
       said measuring step is performed by reading a pressure gauge showing the elevated pressure of the gas that yielded the substantially stationary dialyzate meniscus, the elevated pressure of the gas being substantially equivalent to the osmotic pressure of the sample.  
     
     
       12. A method as recited in claim  11 , said measuring step further comprising the step of: 
       performing a hydrostatic pressure correction based on the height of the solution in the sample cell in the height of the dialyzate in the dialyzate exit tube.  
     
     
       13. A method as recited in claim  2  wherein: 
       said measuring step is performed by reading a pressure gauge showing the elevated pressure of the gas that yielded the substantially stationary dialyzate meniscus, the elevated pressure of the gas being substantially equivalent to the osmotic pressure of the sample.  
     
     
       14. A method as recited in claim  13 , said measuring step further comprising the step of: 
       performing a hydrostatic pressure correction based on the height of the solution in the sample cell in the height of the dialyzate in the dialyzate exit tube.  
     
     
       15. A method as recited in claim  5  wherein: 
       said measuring step is performed by reading a pressure gauge showing the elevated pressure of the gas that yielded the substantially stationary dialyzate meniscus, the elevated pressure of the gas being substantially equivalent to the osmotic pressure of the sample.  
     
     
       16. A method as recited in claim  15 , said measuring step further comprising the step of: 
       performing a hydrostatic pressure correction based on the height of the solution in the sample cell in the height of the dialyzate in the dialyzate exit tube.  
     
     
       17. A method as recited in claim  8  wherein: 
       said measuring step is performed by reading a pressure gauge showing the elevated pressure of the gas that yielded the substantially stationary dialyzate meniscus, the elevated pressure of the gas being substantially equivalent to the osmotic pressure of the sample.  
     
     
       18. A method as recited in claim  17 , said measuring step further comprising the step of: 
       performing a hydrostatic pressure correction based on the height of the solution in the sample cell in the height of the dialyzate in the dialyzate exit tube.  
     
     
       19. A method as recited in claim  1  further comprising the step of: 
       collecting the dialyzate passing through the membrane in a dialyzate collector and flowing the dialyzate therefrom to the transparent dialyzate exit tube.  
     
     
       20. A method as recited in claim  1  further comprising the step of: 
       collecting the dialyzate passing through the membrane in a meandering dialyzate cell and flowing the dialyzate therefrom to the transparent dialyzate exit tube.  
     
     
       21. A method as recited in claim  8  further comprising the step of: 
       collecting the dialyzate passing through the membrane in a dialyzate collector and flowing the dialyzate therefrom to the transparent dialyzate exit tube.  
     
     
       22. A method as recited in claim  8  further comprising the step of: 
       collecting the dialyzate passing through the membrane in a meandering dialyzate cell and flowing the dialyzate therefrom to the transparent dialyzate exit tube.